A drill rig is comprised of a series of pipes all rotated by a rotating means above the ground. The lowermost pipe carries the rotated drilling tool. During the operation of the drill rig, a process sometimes known as inverse circulation is used in which sludge produced by an earth cutting or rock drilling tool is channeled out of the hole through the interiors of a row of drilling pipes. In this process, the hole being drilled is kept filled with water up to ground level. Usually, the water fed to the hole comes from a pond or reservoir and gradually either seeps into the hole or is pumped there. The sludge that is produced during the drilling in the water filled hole is conducted through the pipes of the drill rig to the ground surface level. Usually, a suction pump draws out the sludge. The withdrawn sludge is transferred to that pond or reservoir that supplies the water, thus establishing a continuous fluid circuit during the drilling operation.
In another technique for removing sludge, means are provided for injecting air into the drilling pipes near the bottom of the series of pipes. The air and sludge mix together, and the sludge becomes aerated, it loses its density and its lifting speed increases. In some cases, it is not even necessary to use the suction pump to remove the sludge to the pond or reservoir.
The series of pipes of which a drill is comprised includes an uppermost rotating or Kelly bar beneath which is arrayed the row of extension rods which eventually connect to the drill bit at the lower end. As the drill cuts deeper into the hole, additional pipe sections must be installed. To effect this, the uppermost rod section beneath the rotating or Kelly bar is disconnected from that bar and an additional pipe section is installed between the rotating or Kelly bar and the previous uppermost pipe section. The pipe sections and rotating or Kelly bar are secured together and drilling is continued with the now longer pipe assembly. During the time that the Kelly or rotating bar is disconnected, water or sludge then in the Kelly or rotating bar runs out its bottom end. The previously primed suction pump is no longer primed. It is thus necessary to prime the suction pump again, causing a loss of time in the drilling operation. Further, air will now be drawn through the pipe connections, creating further difficulties until the pump and the entire pipe system is eventually primed again.